PEG-modified RBCs are resistant to invasion by

P falciparum malaria. Control and PEG-modified RBCs were assessed for their abilities to be invaded by P falciparum malaria parasites. Parasites were synchronized to the schizont stage of development and diluted with either control RBCs or PEG-modified RBCs. After a 16-hour incubation, blood smears were prepared, and ring-form parasites were counted. There is a dose-dependent inhibition of parasite invasion using RBCs treated with varying concentrations of both the 3.35 kd PEG derivative (■) and the 18.5 kd PEG derivative (▪). Error bars indicate the standard deviation of 3 determinations. Percentage inhibition of invasion was determined by comparing the number of ring-forms in PEG-modified RBCs to the number of ring-forms in control RBCs as follows: Control RBC ring-forms − PEG RBC ring-forms/Control RBC ring-forms × 100.